What is Space made of?

[Boltzmannbrain]

46 minutes ago, Lorentz Jr said:

Why is this thread in the Relativity section? The question is profoundly speculative, and there are nontrivial answers associated with other theories. If anything, relativity seems to inherit the classical model of space as an empty void that particles move through, only acknowledging that it can be curved and not that it can be made of anything that has a state of motion.

But doesn't it "expand" and "contract" at the speed of light?  That is kind of like moving isn't it?

[Lorentz Jr]

36 minutes ago, Boltzmannbrain said:

But doesn't it "expand" and "contract" at the speed of light?  That is kind of like moving isn't it?

Yes, there's definitely something going on in space that goes far beyond the static nothingness of the vacuum in Newtonian physics. But the principle of relativity states that space doesn't have any "parts" or "constituents" that could have a detectable velocity, which is a property that's normally associated with things that are "made of something".

[crazzy__physicist]

People shuldnt ask such secret questions! 

Edited December 20, 2023 by crazzy__physicist

[chron44]

 

Hi, this thread was started in 2015 and has both puzzled and intrigued lot of posters here in Science Forums. Obviously, its's a subject which established, and "modern" physics has "indications" on, mainly from math in different sections of physics (GR, SR, QFT, SM, and so on).

Still, the apparent quest "What is space made of?" first looks like a philosophical question, but when incorporating modern physics this issue converts to a rather legitimate and straight matter for all levels of physicists.

This situation of today's puzzled stand probably is generally built from the introduction of Minkowski's space cone and the continuation with Einstein's and other physicists' concept of "spacetime" where space and time, both not so easy concepts, were mixed into rather or most complex mathematics.

Probably, with fair reasoning, some of the posters here in this thread have made their own physical/ philosophical statements which "goes like the cat round the hot meal". Because this issue, to my view is both easy and complicated. And postulated or stated, Space itself can only be seen for an imaginary reference entity. -So, Space isn't made of anything. The physics math, isn't wrong either, because this math is a metaphor for Space (and other units) seen in a physics evolving tradition for to comprehend the world we live in.

Being a physics site ppl ask for proof of the statement that Space is an important reference unit or entity. How can one prove this statement? For the moment I cannot do so. -Merely refer to other posts here in this thread, where some have expressed similar or adjacent ideas and thoughts.

Still, if trying to prove that Space isn't made of anything, one can divide on matter and energy (fields) versus space. Space seems to be occupied with matter and energy fields. -Space itself is just a void that hold matter/ energy. Probably this isn't a justified proof of this subject. The proof lies somewhere in all the ppl who have made statements about this. The proof is the resulting collective statement by physics interested folks and professionals. Observe that novel physics mathematics only is a path to a more comprehensive understanding of the world and the universe.

/chron44

 

[TheVat]

8 hours ago, chron44 said:

The proof lies somewhere in all the ppl who have made statements about this. The proof is the resulting collective statement by physics interested folks and professionals.

That's not how proof works.  It doesn't come from a statistical sampling of opinions and interpretations.  A qualified "best explanation based on presently available data" proof would come from experiment and observation.  Science is empirically based.

Since General Relativity, observation has shown that spacetime is geometrically distorted near gravitationally significant masses, pointing to it not being simply an empty void.

 

[chron44]

14 hours ago, chron44 said:

Space seems to be occupied with matter and energy fields.

This is my general conclusion of this thread.

Can anyone counter prove this statement?
(Is it possible at all to do so?)

/chron44

 

[TheVat]

35 minutes ago, chron44 said:

Space seems to be occupied with matter and energy fields.

My two cents worth:

There is just particles and particle events.  Space supplies a metric concept, a volume in which those events can be located and mapped.  Particles will move in that volume "as if" it is curved near a significant mass, but I see no reason to think that there is actual space-stuff.  No aether.  No rubber.  Fields are just a volume whose points have a measurable physical quantity associated with them, either a number or a vector depending on the type of field, so they are just a conceptual thing like "space" - a volume where matter/energy has an influence of some kind and we can measure it at specific locations.

 

[MigL]

16 hours ago, chron44 said:

Space seems to be occupied with matter and energy fields.

In QFT ...  yes.
There are excitations of the various fields which are perceived as virtual particles, or if above a quantum of energy, as real particles.
In QFT, these fields require a background stage to act on.
GR, on the other hand, has no background stage; space-time is an active participant.

But it seems your OP was awfully large to state something which could be summarized by yourself in one line

16 hours ago, chron44 said:

Space seems to be occupied with matter and energy fields.

And ... ???

[StringJunky]

7 hours ago, TheVat said:

My two cents worth:

There is just particles and particle events.  Space supplies a metric concept, a volume in which those events can be located and mapped.  Particles will move in that volume "as if" it is curved near a significant mass, but I see no reason to think that there is actual space-stuff.  No aether.  No rubber.  Fields are just a volume whose points have a measurable physical quantity associated with them, either a number or a vector depending on the type of field, so they are just a conceptual thing like "space" - a volume where matter/energy has an influence of some kind and we can measure it at specific locations.

 

I think so too. Space is that which is occupied by matter and matter is that which occupies space, in the same sense that matter tells space how to curve and space tells matter how to move. They are inextricable.

Per Markus, some years ago: "Spacetime is the map, not the territory". It's a conceptualization of a geometrical arena, with volumetric and temporal axes, to describe energy-density-momentum through time of phenomena within it in some arbitrary volume.

The ontological nature - what something is intrinsically - can never be known, only what it does. Trying to get a macro-materialistic sense of things outside of our senses is futile.

Edited August 4 by StringJunky

[chron44]

6 hours ago, MigL said:

23 hours ago, chron44 said:

Space seems to be occupied with matter and energy fields.

In QFT ...  yes.
There are excitations of the various fields which are perceived as virtual particles, or if above a quantum of energy, as real particles.
In QFT, these fields require a background stage to act on.
GR, on the other hand, has no background stage; space-time is an active participant.

 

Isn't this post from MigL just like the saying by Confucius (which StringJunky uses) here we got two ways of narrative or definitions for "Space". Space is seen in two somewhat different manners - so we cannot be sure of how space is constructed in a general sense.

In QFT the statement from me seems to be lucid.

In GR, for example, this statement is not that comprehensive.

???

It seems like the original issue "What is Space made of?" has two somewhat different outcomes (at least in physics).

 

[externo]

Space is the ether, this has been known since 1900. Even in Einstein's theory, which removes the rest frame, space is the 4-dimensional ether.

Matter is ether in a condensed form.

Edited August 4 by externo

[studiot]

38 minutes ago, externo said:

Space is the ether, this has been known since 1900. Even in Einstein's theory, which removes the rest frame, space is the 4-dimensional ether.

Matter is ether in a condensed form.

I don't think you will find many in agreement with these claims.

[externo]

26 minutes ago, studiot said:

I don't think you will find many in agreement with these claims.

About the space I find at least Einstein himself :

Quote

Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this ether may not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it.

https://en.wikisource.org/wiki/Ether_and_the_Theory_of_Relativity

 

A possibility about the nature of space would be some kind of crystal :

https://www.qeios.com/read/RDW13U

Quote

We present quaternion quantum mechanics and its ontological interpretation. The theory combines the Cauchy model of the elastic continuum with the Planck-Kleinert crystal hypothesis. In this model, the universe is an ideal elastic solid where the elementary particles are soliton-like waves. Tension induced by the compression and twisting of the continuum affects its energy density and generates the force of gravity, as density changes alters the wave speed and hence gravity could be described by an index of refraction.

 

Edited August 4 by externo

[studiot]

2 hours ago, StringJunky said:

Space is that which is occupied by matter and matter is that which occupies space,

Are you suggesting that you cannot have unoccupied space ?

 

I think a good question to consider is " Is there any (detectable) difference between occupied and unoccupied space ?"

Another good one is the Principle of Least Energy, which appears to be in force at all scales and is the justification for Higgs Theory at the smallest.

[StringJunky]

23 minutes ago, studiot said:

Are you suggesting that you cannot have unoccupied space ?

 

I think a good question to consider is " Is there any (detectable) difference between occupied and unoccupied space ?"

Another good one is the Principle of Least Energy, which appears to be in force at all scales and is the justification for Higgs Theory at the smallest.

Unoccupied space at what level? That's semantics, depending on what one is focusing on. All space has matter in it. If the space didn't have matter in it there would be no space, since space is the distance between things or that volume a thing occupies. No definition can be all inclusive... to define means to distinguish i.e delineate, or we might as well say 'Universe' to cover every possible instance.  

Edited August 4 by StringJunky

[studiot]

26 minutes ago, StringJunky said:

Unoccupied space at what level? That's semantics, depending on what one is focusing on. All space has matter in it. If the space didn't have matter in it there would be no space, since space is the distance between things or that volume a thing occupies. No definition can be all inclusive... to define means to distinguish i.e delineate, or we might as well say 'Universe' to cover every possible instance.  

So what's in the distance between things ?

[StringJunky]

5 minutes ago, studiot said:

So what's in the distance between things ?

Space aka volume. Distance is a 1D abstraction of space. Space as something material depends on what you want to look at within that volume.

[studiot]

54 minutes ago, StringJunky said:

Space aka volume. Distance is a 1D abstraction of space. Space as something material depends on what you want to look at within that volume.

Since we don't live in an Anne McAffrey 'Pern'  universe and space is what lies between things, why is that space not 'unoccupied' ?

 

[StringJunky]

27 minutes ago, studiot said:

Since we don't live in an Anne McAffrey 'Pern'  universe and space is what lies between things, why is that space not 'unoccupied' ?

 

We can talk about space between things and things that occupy space, depending on the focus. 'Space' is just an abstraction to delineate an object within it or outside of it, or the whole inclusive volume. A space is occupied, or not, depending what your focus is. Are their 'actors' in it or not. This is turning into a tautology.

[dimreepr]

19 minutes ago, StringJunky said:

This is turning into a tautology.

It's often the only explanation that work's.

[studiot]

52 minutes ago, StringJunky said:

We can talk about space between things and things that occupy space, depending on the focus. 'Space' is just an abstraction to delineate an object within it or outside of it, or the whole inclusive volume. A space is occupied, or not, depending what your focus is. Are their 'actors' in it or not. This is turning into a tautology.

I'm banging on about 'empty space' for a reason.

Back along Mordred mentioned symmetry breaking and I mentioned Higgs and the Principle of Least Energy.

 

This is because using our best standard model equations Higgs' great insight was to show that 'empty space' is in an energetically higher state than space permeated by what we now call the Higgs Field ie non empty.

It would seem that Nature does indeed abhor a true vacuum.

[StringJunky]

33 minutes ago, studiot said:

I'm banging on about 'empty space' for a reason.

Back along Mordred mentioned symmetry breaking and I mentioned Higgs and the Principle of Least Energy.

 

This is because using our best standard model equations Higgs' great insight was to show that 'empty space' is in an energetically higher state than space permeated by what we now call the Higgs Field ie non empty.

It would seem that Nature does indeed abhor a true vacuum.

Ok. The Higgs field is what contributes to mass?

[studiot]

36 minutes ago, StringJunky said:

Ok. The Higgs field is what contributes to mass?

Yes indeed, but more than that, the higgs field is the gage field that supports the higgs boson which is the particle that is responsible for mass.

Higgs didn't invent the idea that was originally due to Nambu (1957) who showed how the mass gain of cooper pairs in superconductivity are a result of a symmetry breaking mechanism.
Higgs applied this to his new field to derive the mass boson.

Edited August 4 by studiot

[MigL]

Possibly a lot of the misconceptions can be attributed to mixing up models.
GR and QFT treat space-time differently.
In QFT, space-time is the stage on which various fields act.
In GR, space-time is an active participant, and no background stage is required for the acting.
I find it funny when one uses the quantum mechanical considerations of a crystal, to make predictions about the properties of the aether that ( they believe ) permeates space in GR.

And I'm with Studiot ( as always ) on this.
You can't define space by the matter within it, and then say "there is empty space between matter". How, then, is that 'empty' space between matter defined ?

We would do well to stop trying to force reality to be the same as our models ( GR and QFT ). All our models do, is describe small parts and qualities of reality, and only within their range of applicability.

[geordief]

15 minutes ago, MigL said:

We would do well to stop trying to force reality to be the same as our models ( GR and QFT ). All our models do, is describe small parts and qualities of reality, and only within their range of applicability.

Definitely. We have to take things as we find them.

 

What is the connection between space-time and space?

Is space timeless? A 3d surface in 4d space-time?

 

Just because I was wondering ,do excitations of the fields attract gravitationally ?(think the answer should be  "yes") 

Edited August 4 by geordief